The present invention relates to motion control systems and, more specifically, to motion control systems including a track segment for linear motor drive systems supporting movers on tracks in which switches corresponding to drive coils are controlled to electromagnetically propel the movers along the track.
Motion control systems utilizing movers and linear motors can be used in a wide variety of processes (e.g. packaging, manufacturing, and machining) and can provide an advantage over conventional conveyor belt systems with enhanced flexibility, extremely high speed movement, and mechanical simplicity. The motion control system includes a set of independently controlled “movers” each supported on a track for motion along the track. The track is made up of a number of track segments or sections that, in turn, hold individually controllable electric coils. Successive activation of the coils establishes a moving electromagnetic field that interacts with the movers and causes the mover to travel along the track. Sensors, such as Hall Effect sensors or Magnetoresistance sensors, may be spaced at fixed positions along the track and/or on the movers for detecting opposing magnets to provide information about the position and speed of the movers.
Each of the movers may be independently moved and positioned along the track in response to the moving electromagnetic field generated by the coils. In a typical system, the track forms a closed path over which each mover repeatedly travels. At certain positions along the track other actuators may interact with each mover. For example, the mover may be stopped at a loading station at which a first actuator places a product on the mover. The mover may then be moved along a process segment of the track where various other actuators may fill, machine, position, or otherwise interact with the product on the mover. The mover may be programmed to stop at various locations or to move at a controlled speed past each of the other actuators. After the various processes are performed, the mover may pass or stop at an unloading station at which the product is removed from the mover. The mover then completes a cycle along the closed path by returning to the loading station to receive another unit of the product.
A DC (Direct Current) power supply is typically used to provide DC power to sections in the system. The DC power supply typically provides a full-bus DC power rail (“full-bus”), a mid-bus DC power rail (“mid-bus”) equal to about half the full-bus, and a DC reference. To propel the movers, switches are used to activate the drive coils with varying polarities and magnitudes between the full-bus and the DC reference, with currents bi-directionally sourcing or sinking with respect to the mid-bus. It is desirable to continuously improve the efficiency of this system where possible.